Adam Driver and Scarlett Johansson fall apart in the tender, devastating Marriage Story

Marriage is an enormous act of faith; it has to be, statistically — what else asks you to give your whole heart, with a 50 percent chance it might be pulverized?

Noah Baumbach’s Marriage Story is an act of faith too: a bet that you’ll watch two ordinary (albeit exceptionally attractive) people fall apart, like uncountable couples before and after them. There isn’t even really some hugely dramatic schism between Charlie (Adam Driver) and Nicole (Scarlett Johansson) that triggers it all; just the everyday alienations and betrayals of a union that seems to be working, until it suddenly isn’t anymore.

But their unraveling turns out to be a sad, funny, devastating thing to watch unfold; a sort of pulverization-by-proxy that draws you so far into Charlie and Nicole’s world, it sometimes feels like trespassing just to be there in the theater.

The script lets you know from the outset that they were very much in love once, this brilliant Brooklyn theater director and his actress muse, with their wild creative collaborations and adorable young son (Azhy Robertson). But when Nicole has a shot at a TV pilot in Los Angeles, where she also grew up, she sees it as a chance to get out from under Charlie; the weight of his opinions and assumptions and his monumental (to her) self-absorption. He’s shellshocked — confounded that she would leave what they have, their New York life and their artistic freedom, for the palm-treed banality of Hollywood.

Soon, there are lawyers: A shark in stilettos for her (a shrewd, fantastic Laura Dern), and a tag team of rumpled semi-retiree (Alan Alda) and ruthless goodfella (Ray Liotta) for him. Questions about which coast they’ll settle on and who will have more custody of their son get ugly fast; their promises to keep it amicable pretty much disappear with the zeroes on their first legal bill.

As Baumbach navigates the growing breach between them, he lets the movie’s rhythms ebb and flow; there are long scenes where nothing much happens, other than ordinary life, and others where the hurt and animosity explode, years of pent-up feeling packed into a single look or an angry word that can’t be taken back.

Johansson is extremely watchable, if a little opaque, as Nicole — though that’s fitting, maybe, for a character who confesses she’s never really known who she is without her family. Truly, the movie belongs to Driver, who puts so much raw, tender feeling into Charlie that even his worst moments evoke at least some pang of empathy.

Maybe that’s an unfair game on Baumbach’s part as well, if he is in fact drawing from his own life (he and the actress Jennifer Jason Leigh were divorced in 2013, and also share a son); but Story is his story to tell, and tilt however he wishes. And though it may not an easy movie to watch, or even a particularly original one — there’s still Kramer vs. Kramer, after all — Marriage still feels like something special on the screen: a movie that somehow makes its intimacy seem like a radical act, one messy, heart-wrecking moment at a time. A–

(Marriage Story is playing this week at the Toronto International Film Festival; it comes to theaters Nov. 6 and Netflix Dec. 6)